1. Field of the Invention
The present invention relates to a connection structure for a noise reduction impedance element, a noise reduction impedance element positioning method, and a recording medium having a noise reduction impedance element positioning program recorded therein.
2. Description of the Related Art
Faster electronic circuits produce stronger radiated noise, leading to demands for more effective noise reduction. Typically, resistors, inductors, capacitors, and the like are employed to achieve noise reduction. When a single component does not provide sufficient noise reduction, composite components, such as a combination of an inductor and a capacitor, are used.
In general, noise reduction components are connected at a transmission side of an electronic device (noise source). This is because a noise reduction component which is electrically connected to a transmission side is said to provide higher noise suppression performance. Sometimes, electronic devices (noise sources) are connected to both ends of a signal cable so that an RF signal is transmitted/received via the signal cable. In this case, noise reduction components may be connected in the vicinity of cable connectors located at both ends of the signal cable.
Recently, the demand for low power consumption electronic circuits has increased, and impedance elements such as resistors or inductors, which do not include capacitors which causes a relatively high power consumption, tend to be used as noise reduction components to achieve noise reduction. However, if impedance elements such as resistors or inductors only are used, there is a noise frequency which is not attenuated unless the impedance of the impedance elements increases. However, increased impedance leads to a problem in that an RF signal waveform is increasingly distorted, leading to incorrect operation.
It is an object of the present invention to provide a connection structure for a noise reduction impedance element, a noise reduction impedance element positioning method, and a recording medium having a noise reduction impedance element positioning program recorded therein, thereby providing high noise reduction performance.
To this end, in one aspect of the present invention, a noise reduction impedance element connection structure includes a transmission path for providing an electrical connection between a first electrical element, such as a signal output IC, and a second electrical element, such as a load IC. A first noise-reduction impedance element electrically connected to the transmission path at a first location thereon, such as the signal output IC of the transmission path, and a second noise-reduction impedance element is electrically connected to the transmission path at a second location thereon, such as the load IC of the transmission path. The first location corresponds to the current peak of a noise frequency that exceeds a predetermined limit when the first noise-reduction impedance element is electrically connected to the transmission path. The noise reduction impedance elements maybe impedance elements, such as resistors, inductors, or common mode choke coils, but do not include capacitors.
In another aspect of the present invention, a noise reduction impedance element positioning method includes the steps of: (a) electrically connecting a first noise-reduction impedance element to a signal output IC of the transmission path, the transmission path providing an electrical connection between the first electrical element, such as the signal output IC, and a second electrical element, such as a load IC; (b) determining whether or not a numerical value obtained by one of a measurement and a calculation using simulation with respect to a noise frequency satisfies a predetermined limit; (c) identifying a noise frequency in excess of the predetermined limit; (d) determining a location corresponding to the current peak of the noise frequency in excess of the predetermined limit by one of the measurement and the calculation using simulation; and (e) electrically connecting a second noise-reduction impedance element at the location corresponding to the current peak.
In still another aspect of the present invention, a recording medium contains a program implementing a noise reduction impedance element positioning process by a computer, the process including the steps of: entering the name of a first noise-reduction impedance element and the name of a second noise-reduction impedance element, the first noise-reduction impedance element being electrically connected to a transmission path at a first location thereon, such as to a signal output IC on the transmission path, the second noise-reduction impedance element being electrically connected to a second electrical element, such as a load IC on the transmission path, the transmission path providing an electrical connection between the first and second elements; determining a location corresponding to the current peak of a noise frequency that exceeds a predetermined limit when the first noise-reduction impedance element is electrically connected to the transmission path; determining a noise characteristic of the transmission path to which the first and second noise-reduction impedance elements are connected, the second noise-reduction impedance element being connected at the location corresponding to the current peak; and determining whether or not the noise characteristic satisfies the predetermined limit.
Accordingly, first, a first noise-reduction impedance element is electrically connected to a transmission path. A noise frequency that exceeds a predetermined limit when the first noise-reduction impedance element is connected is measured or calculated by simulation to find the current peak. Further, a second noise-reduction impedance element is electrically connected to the transmission path at a location corresponding to the current peak. Therefore, radiated noise on the transmission path can be effectively reduced without using a capacitor.